This invention relates generally to a commutator housing for an electric motor including an overcurrent protection device and a method for producing the commutator housing. In particular, the invention relates to an electric motor designed to drive automobile equipment, such as a vehicle window regulator, sunroof or seat operation actuator.
A commutator usually includes a commutator ring having a series of conductive segments around its circumference. The commutator ring is designed to be mounted integrally with a rotor shaft. An electric motor generally includes a stator frame and a rotor mounted rotatably in the stator. The motor also includes windings integral with the rotor shaft, and each winding is electrically connected to two diametrically opposed segments of the commutator.
The commutator is generally mounted in a commutator housing integral with the stator. The commutator housing includes a support having a central opening designed to receive the commutator and to allow the rotor shaft to pass through the housing support. The support is made of an insulating material, such as plastic. The commutator housing also includes at least one pair of brush holders, diametrically opposite the commutator, which are designed to receive brushes to make contact with the segments of the commutator during rotation with the rotor shaft. The brushes are electrically connected to an electrical power supply.
Generally, one of the brush holders is directly connected via a connection track to a pin of a power supply connector, while at least one other brush holder is connected to another pin of the power supply connector via an overcurrent protection device. The overcurrent protection device is intended to protect the brushes from possible overheating due, for example, to excess current or extreme weather conditions.
Such an overcurrent protection device may include heat dissipating transistors, a conductive chemical compound or a stacked structure. For example, a heat protection device can be produced using chemical compounds extruded and placed between two sheets of nickel which are then cut out. Iron/copper electrodes are added to the cut out sheets to adjust transfer time of the overcurrent protection device to a desired value.
The overcurrent protection device is generally mounted on the commutator housing by soldering it into a conductive line or track. There is a break in the conductive track, and tabs are soldered at each end of the break in the conductive track. The tabs at the break in the track are generally installed by the supplier of the commutator housing. The commutator housing can be placed directly on a printed circuit board provided with brush holders and tabs to receive the overcurrent protection device. The overcurrent protection device is then soldered to these tabs to form a series component in the conductive track that connects one of the brush holders to one of the power supply pins. Electrical continuity between the brush and the power supply connector is ensured via the overcurrent protection device, which can effectively limit or dissipate overheating of the system without interrupting electrical conduction.
Soldering the overcurrent protection device into a conductive track requires the use of soldering equipment to assemble the commutator housing.
A need exists for a commutator housing equipped with an overcurrent protection device that can be assembled onto the commutator housing without requiring a soldering stage, allowing for the elimination of the soldering equipment from the commutator housing assembly process.